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Does the influence of the epibenthic predator Crangon crangon L. (brown shrimp) extend to sediment microalgae and bacteria?
Jönsson, B.; Sundbäck, K.; Nilsson, P.; Lindstrom Swanberg, I.; Ekebom, J. (1993). Does the influence of the epibenthic predator Crangon crangon L. (brown shrimp) extend to sediment microalgae and bacteria? Neth. J. Sea Res. 31(1): 83-94
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Jönsson, B.
  • Sundbäck, K.
  • Nilsson, P.
  • Lindstrom Swanberg, I.
  • Ekebom, J.

Abstract
    The effect of juvenile Crangon crangon L. (brown shrimp) on the microbial part of the food web of marine shallow-water sandy sediment was investigated in two experiments using an outdoor flow-through system. Biomass, composition and productivity of microalgae and bacteria, POC and PON content in the sediment, as well as nutrient and oxygen fluxes were measured in the absence and presence of two natural densities (50 and 100 ind·m-2) of juvenile Crangon. Stimulating effects of the presence of juvenile Crangon on both microalgae and bacteria were observed after three weeks. However, the number of statistically significant effects was low, despite the conspicuous change in sediment characteristics caused by Crangon activity. To explain the possible trophic effect of Crangon via meiofaunal grazing, the results were compared with meiofaunal grazing rates (dual labelling by 14C- bicarbonate and 3H-thymidine) and changes in the meiofaunal and macrofaunal community. The reasons for the low number of significant trophic effects of Crangon on algae and bacteria were that the overall meiofaunal grazing pressure on microbiota was low, and that only part of the meiofauna (mainly harpacticoid copepods) was significantly affected by the predator. Meiofauna thus appeared to be a weak mediating link in the sandy sediment system investigated. No effect of Crangon on oxygen fluxes, or POC and PON content in the sediment was observed. Neither were the nutrient concentrations in the overlying water affected, but increased nutrient levels in the pore water were observed. According to theoretical calculations, excretion from the shrimp may imply a considerable nutrient addition which can be rapidly re-utilized by the microbes directly at the sediment/water interface. Bio-turbation by Crangon appeared to counteract flaking of the microalgal mat.

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